As information technology has rapidly progressed, computer network centers such as server farms and server clusters have become increasingly important to our society. The server farms provide efficient data processing, storage, and distribution capability that supports a worldwide information infrastructure, which has come to dominate how we live and how we conduct our day to day business.
Typically, at a site where numerous computers are connected to a network, the computers and related equipment are stacked in racks, which are arranged in repeating rows. In conventional systems, the racks are configured to contain computer equipment having a standard size in compliance with the Electronic Industries Alliance (“EIA”) “rack unit” or “U” standard. Each computer would have a height of 1U, 2U, or some U-multiple, with each U corresponding to approximately 1.75″.
FIG. 1 shows a conventional rack 100 measuring roughly 19 inches wide, 30 inches deep and 74 inches high. This rack 100 is formed of a rectangular frame structure having four vertical supports 102 (two in the front and two in the back), each support 102 having a plurality of holes 104 (typically rectangular) formed along its length. Horizontal rails, which are used to support each individual component to be mounted in the rack, are attached to the vertical supports 102 using cage nuts that are passed through the holes in the supports. Walls may be attached to the sides and top of the frame structure and doors may be provided on the front side 105a and back side 105b in order to provide a complete enclosure for the rack system.
Each computer mounted in the rack 100 may comprise a computer chassis supporting a main board. The main board may be alternatively referred to as the motherboard or system board. The main board comprises the primary printed circuit board (PCB) of a computer. The basic circuitry and components used by a computer to function are generally either contained in or attached to the main board. The main board typically contains the system bus, processor and coprocessor sockets, memory sockets, serial and parallel ports, expansion slots, and peripheral controllers.
By providing the vertical supports with a plurality of holes, a great deal of flexibility in the placement of the horizontal rails can be achieved. Accordingly, a wide variety of heights of components can be accommodated by the rack frame structure. However, the manual positioning and installation of each rail can be a time-consuming and labor-intensive process, significantly increasing the total cost of the system.
A recent trend in rack-based computer systems has been towards increasing the density of computers that will fit into each rack. This increase in density has been achieved by decreasing the height of each computer, while maintaining the width and depth dimensions of the computer so that the computer can still be mounted into a conventional computer rack. Thus, each computer chassis is made very wide, very deep, and very short, often just 1U in height. The motherboard that is contained in each computer is typically a relatively flat printed circuit board which can be easily placed into such a wide, deep, and flat computer chassis. However, layout difficulties arise when trying to add the additional components which are either mounted onto or attached to the motherboard to form a functional computer. These components include, for example, hard drives, removable media drives, power supplies, microprocessors, microprocessor heat sinks, fans, and memory. Because of the low profile of the computer chassis, there is very little room above the motherboard for positioning these components. Generally, the motherboard has a footprint (i.e., width and depth of the motherboard) that is significantly smaller than the footprint of the computer chassis. Thus, these other components are typically positioned in the space available in the chassis adjacent to the motherboard. However, the short height of the chassis limits the number and size of components that can be placed here.
The dense packing of components in these low-profile computer chassis presents cooling problems as well. Rack-based computer systems are typically cooled by directing air through each computer chassis in a front-to-back direction. Because the 1U computer chassis are so thin, any component contained within the computer chassis can significantly impede the flow of air through the computer chassis and across all of the components. This can produce “hot spots”, which are regions that do not receive sufficient airflow, thereby enabling heat to accumulate.
This airflow problem can be particularly problematic when attempting to cool the main processor or processors in the computer. Many processors (sometimes referred to as a “central processing unit” or “CPU”) generate tremendous amounts of heat during operation and are provided with heat sinks to dissipate this generated heat. These heat sinks may be passive heat sinks, which cool the processor by conducting the heat away from the processor using fins. The heat can then be drawn away from the fins and out of the chassis by the cooling airflow. Alternatively, the heat sinks may be active heat sinks, which actively draw heat away from the processor, using, for example, dedicated processor fans. In either case, the heat sink increases the overall thickness of the processor assembly. In some cases, when the processor and heat sink are mounted onto a motherboard, the overall assembly is over 1.75″ thick, preventing its use in 1U chassis systems. Even when the processor and heat sink are sufficiently thin that they can fit into the chassis, there is very little additional clearance around the heat sink, thereby preventing cooling air from effectively cooling the processor. Furthermore, the dense packing of additional components can also impede the flow of air across the processor and heat sink. Accordingly, the progression towards increasing thin rack-based computers has produced both packaging and cooling problems for some computer systems.
Another problem which faces operators of rack mounted computer systems is the difficulty of servicing the computers for repairs or upgrades. Conventional rack mounted computer components may be provided with flanges that extend from the sides of the front face of the computer chassis. Each of these flanges may be configured with two mounting holes which can be aligned with the holes 102 provided on the vertical supports 102 of the rack 100. A pair of screws or bolts may be passed through these aligned holes in each flange in order to secure the computer to the rack 100. Thus, each time the computer chassis is mounted in the rack, these screws need to be attached, and each time the computer chassis is removed, these screws must be detached.